1. Field of the Invention
The present invention relates to a thermosensitive recording material, and particularly to a thermosensitive material having superior anticurling properties and having a proper coefficient of friction.
2. Description of the Related Art
Thermosensitive materials in which heat is provided by a thermal head or the like to record images are relatively cheap, and recording devices for use therewith are simple, highly reliable, and maintenance-free. Accordingly, the thermosensitive materials are widely used. In recent years, attempts are especially being made to realize high image quality and high performance, such as improvements in preservability.
On the other hand, the thermosensitive materials have a problem in quality in that an elongation balance between front and back surface layers of the thermosensitive recording material is lost due to a change in environment, such as humidity, or due to application of heat during recording, thereby causing so-called curling, i.e., one surface side of the thermosensitive recording material is deformed in a curled state. In particular, such a phenomenon has been markedly observed in multilayered color thermosensitive recording materials in which plural thermosensitive recording layers having different color development hues are superimposed.
Even when high image quality and high performance, such as improvements in preservability, are realized, such curling extremely impairs product quality as a recording material.
In order to prevent such curling from occurring, in addition to a thermosensitive recording layer, a protective layer and the like, the thermosensitive recording material is provided with a back coat layer on a surface (back surface) at a side of a support at which the thermosensitive recording layer and the like are not provided. For example, Japanese Patent Application Laid-Open (JP-A) No. 8-282112 discloses a technique for providing on a support a back coat layer comprising a single layer, and including an inorganic stratiform compound in the back coat layer. Certainly, by providing a layer containing the inorganic stratiform compound on the surface opposite to the side having the thermosensitive recording layer, curling of the whole of the recording material is inhibited to some extent. However, curling under a low-humidity environment cannot be completely prevented, thereby causing deformation in the curled state, so that there is still a problem in quality as a recording material. Further, even in a color thermosensitive recording material having a multilayered thick recording layer, curling is liable to occur, so that there is a problem in maintaining flatness.
In particular, in recent years as imaging techniques of various modes have been provided, and colorization of images has progressed and become important, not only realization of high performance, such as high image quality and improvements in preservability, is required, but also that the quality of the material itself as a recording medium is not impaired and is stable. In addition, a range of application may possibly be limited by the curling.
Thus, the present assignee previously proposed in Japanese Patent Application No. 2001-110050 a thermosensitive recording material in which polyvinyl alcohol and water-swelling mica are contained in a back coat layer, and curling by a change in environment, such as humidity, during use or by application of heat during recording can be avoided, and which is free from reduction in quality by deformation of the material and can be applied in a wide range of fields. However, the back coat layer of this thermosensitive recording material has a low coefficient friction. During delivery of many thermosensitive recording materials in a superimposed state, since a thermosensitive recording layer on a front surface of one thermosensitive recording material and the back coat layer of another thermosensitive recording material are slippery, there may be cases where trouble occurs during delivery. Thus, there is still room for improvement.